1. Field of the Invention
This invention relates to a porous ceramic structure and particularly to a porous ceramic structure for collecting carbon particulates exhausted from diesel engines.
2. Description of the Prior Art
The U.S. Pat. No. 4,264,346 and No. 4,415,344 describe porous ceramic structures respectively comprising a multiplicity of inlet passages, of which front ends are open and rear ends are closed, a multiplicity of outlet passages, of which rear ends are open and the ends opposing to the rear ends are closed, and porous walls positioned between the passages.
As illustrated in FIGS. 22 and 23, the inlet passages 52' and outlet passages 53' are positioned next to one another in one type of the structure (U.S. Pat. No. 4,264,346 and No. 4,415,344), and the inlet passages are positioned around outlet passages in another type of the structure (U.S. Pat. No. 4,415,344).
An automobile exhaust gas, for example, first enters the inlet passages 52' and then passes through the porous walls 2' to enter into the outlet passages 53', and then flows out of the structure 1'.
Particulates contained in the automobile exhaust gas or the like are collected by a part of the porous partition walls in these structures.
The intermediate portions of the inlet passages do not collect the particulates efficiently in conventional porous ceramic structures. The particles, however, are collected mostly at the opening end and bottom end of the inlet passages by conventional porous ceramic structures as shown in FIG. 10.
It is considered that the inertia force of the exhaust gas flow causes this inefficiency in conventional porous ceramic structures.
Particulates can not be collected evenly in the conventional structures and the particulates collection efficiency of the conventional structures is not satisfactory.